Dynamic reference method and system for interventional procedures

ABSTRACT

An interventional device configured for placement in or near an internal organ or tissue is provided. The interventional device includes a reference portion having three or more sensor elements. In one implementation, the interventional device and associated sensor elements provide dynamic referencing of the internal organ, tissue or associated vasculature after registration of the sensor data with images and/or volumetric representations of the internal organ or tissue.

BACKGROUND

The present technique relates generally to interventional procedures,such as interventional medical procedures. In particular, the presenttechnique relates to image-guided interventional techniques, such asthose used in conjunction with various radiology procedures.

As medical imaging technologies have matured, it has become possible tocombine the use of medical imaging techniques with the performance ofinvasive procedures. For example, interventional procedures such asbiopsies and tumor ablations may benefit from the use of imagingtechniques that allow a clinician to visualize the target region alongwith the intervention device while the procedure is being performed. Inthis way, the clinician may guide the interventional device to thetarget region with relative accuracy and, perhaps, without unnecessarytissue damage.

In practice, such image-guided interventional techniques typicallyemploy a tracking frame of reference device placed proximate to theanatomy of interest. The reference device moves with the patient toprovide accurate and consistent tracking of the anatomy of interest.Typically, the reference device needs to be rigidly secured to theanatomy of interest. As a result, the reference device is generallyattached to hard bone near the anatomy of interest. As a result, suchimage-guided interventional techniques are generally limited to regionsin the body bounded by bony anatomy, such as cranial neurosurgery,spine, orthopedic, and sinus procedures.

While such techniques are useful, clearly there are other areas of thebody that are not bounded by bony structures and that might also benefitfrom such image-guided techniques. However, regions of the body that arenot bounded by such bony structures, such as cardiac and abdominalregions, currently cannot benefit from such image-guided techniques dueto the inability to affix a reference device proximate to the anatomy ofinterest. Further, many internal organs that might benefit fromimage-guided interventional techniques can move, such as due torespiration, gravity, and so forth, and therefore, present additionalinterventional challenges. In addition, even in regions of the anatomywhere there is proximate bone, it may not be desirable to attach areference device to the bone. Therefore, it is desirable to provide areference technique for image-guided interventional procedures that doesnot require a reference device affixed to skeletal structures.

BRIEF DESCRIPTION

The present technique is generally directed to the dynamic referencingof an internal structure in an image-guide interventional procedure. Inone implementation, an interventional device having three or more sensorelements is provided. In such an embodiment, the interventional deviceis placed on or in an internal structure, such as an internal organ orvasculature, such as during an interventional procedure. Signals orfields generated by the sensor elements, such as electromagnetic signalsor fields, may be used to determine the positions of the sensorelements. The positions of the sensor elements may then be registeredwith a set of image based data which may or may not include image datarepresentative of the sensor elements. In one embodiment, theregistration occurs automatically. Once the signals generated by thesensor elements is registered with the images or volumetricrepresentations of the internal structure, the position and orientationinformation derived from the sensor elements may be used to modify oradjust the visual representation of the internal structure to reflectmotion or deformation of the structure. The modified or adjusted visualrepresentation may then be used to allow a surgeon or other clinician toperform an image-guided invasive procedure based on images reflectingthe current position and shape of the internal structure.

In accordance with one aspect of the present technique, aninterventional device is provided. The interventional device includes areference portion configured for placement proximate to or inside aninternal organ such that the reference portion moves with the internalorgan. The reference portion is not physically attached to the internalorgan when so placed. The interventional device also includes three ormore sensor elements integrated on the reference portion. The three ormore sensor elements are configured to provide at least positioninformation.

In accordance with a further aspect of the present technique, a methodfor tracking dynamic motion of an organ is provided. The method includesthe act of generating a first set of position data for three or moresensor components integrated on a reference portion of an interventionaldevice. The reference portion is placed proximate to or inside of aninternal organ. The first set of position data is based on signals orfields generated by the sensor components. A second set of position datafor the three or more sensor components is generated based on anidentification of the three or more sensor components in one or moreimages or volumetric representations of the internal organ.Corresponding sensor components are identified in the first set ofposition data and the second set of position data. The first set ofposition data is registered with the one or more images or volumetricrepresentations based on the identification of corresponding sensorcomponents in the first set of position data and the second set ofposition data.

In accordance with an additional aspect of the present technique, amethod for tracking dynamic motion of an organ is provided. The methodincludes the act of generating a position and orientation data for threeor more sensor components integrated on a reference portion of aninterventional device. The reference portion is placed proximate to orinside of an internal organ. The position and orientation data is basedon signals or fields generated by the sensor components. A shape modelof the interventional device is generated based on the position andorientation data. A region of interest is segmented in one or moreimages or volumetric representations. The region of interest comprisesat least one of the internal organ, a portion of the internal organ, ora region proximate or connected to the internal organ. A shape model ofthe region of interest is generated based on the segmentation. The shapemodel of the interventional device is registered with the shape model ofthe region of interest.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 depicts an interventional device including sensor components, inaccordance with an exemplary embodiment of the present technique;

FIG. 2 depicts an interventional device inserted into an organ, inaccordance with an exemplary embodiment of the present technique;

FIG. 3 depicts exemplary components of an imaging system and a positiondetermining system, in accordance with an exemplary embodiment of thepresent technique;

FIG. 4 depicts exemplary components of a computed tomography orthree-dimensional fluoroscopy imaging system and a position determiningsystem, in accordance with an exemplary embodiment of the presenttechnique;

FIG. 5 depicts exemplary acts for using a position determining system,in accordance with an exemplary embodiment of the present technique; and

FIG. 6 depicts exemplary acts for using a position determining system,in accordance with a further exemplary embodiment of the presenttechnique.

DETAILED DESCRIPTION

The present technique is directed to dynamic referencing of internalorgans for image-guided interventional procedures. In particular, thepresent technique utilizes an interventional device configured with oneor more tracking devices. The interventional device is configured forplacement next to or in an internal organ of interest such that movementof the organ can be tracked in conjunction with acquired images or imagedata. In particular, in an exemplary embodiment, the movement of thetracking devices is automatically registered with the image data,without the use of anatomical or fiducial markers. In this manner, animage-guided interventional procedure may be performed using the dynamicreference information acquired using the interventional device. Becausethe interventional device can be associated with the anatomy of interestwithout being affixed to bone, the present technique may be suitable foruse with percutaneous procedures performed on internal organs that maymove or be moved and which are not close to a suitable skeletal anchor.Examples of such organs include, but are not limited to the liver,lungs, kidneys, pancreas, bladder, and so forth.

For example, referring to FIG. 1, an interventional device 10 isdepicted that is suitable for placement near, in, or on an organ ofinterest. The interventional device 10 includes a reference portion 14.The reference portion 14 includes three or more sensor elements 16 that,in an exemplary embodiment, may be used to acquire position informationrelating to the reference portion 14. In the depicted embodiment, aconductive element 18 is also provided which may be suitable forproviding power to the sensor elements 16 in implementations in whichthe sensor elements are powered.

For example, in an exemplary embodiment, the interventional device 10 isa catheter 20. An example of such a catheter 20 might be a 7-frenchstraight catheter suitable for introduction via a jugular or femoralvein and for insertion of the tip, here depicted as reference portion14, into the hepatic (or other) vasculature, as depicted in FIG. 2. Insuch an embodiment, the catheter tip may be guided to the hepatic vein24 (or other vein) under fluoroscopy after introduction of a suitablecontrast agent to the blood stream. Once at the liver 26, the tip of thecatheter 20 can be lodged into the hepatic vein 24 such that thereference portion 14 is deep within the liver 26 and in a stableposition. In such an implementation, because the liver 26 movesessentially as a rigid body during respiration and because the referenceportion 14 is lodged within the hepatic vein 24, the reference portion14 will move with the liver 26. Because the reference portion 14 willmove with the liver 26, the reference portion 14 can act as a dynamicreference with regard to the liver 26. As a result, an interventionalprocedure, such as insertion of a biopsy needle 28 into a structure ofinterest 30, can be performed using image-guided techniques usingposition or motion information obtained using the sensor elements 16integrated on the reference portion 14.

Typically, the sensor elements 16 are not provided in a lineararrangement, i.e., the sensor elements 16 do not form a single line,such that the respective sensor elements 16 can be distinguished fromone another based upon their known spatial relationships. For example,in the exemplary depicted embodiments of FIGS. 1 and 2, the sensorelements 16 are provided on a curved portion of the catheter 20 suchthat the information received from the sensor elements 16 can be used todistinguish the respective sensor elements 16 from one another based onknown spatial and/or geometric relationship of the sensor elements 16 toone another.

In one embodiment, the sensor elements 16 are provided aselectromagnetic (EM) microsensors, such as solid or hollow EM coils,that are integrated into or securely attached to the interventionaldevice 10. In implementations employing such EM coils, each EM sensorcoil can provide information regarding the orientation of the respectivecoil in two directions. In one embodiment, however, a single coil cannotprovide sufficient information to determine the roll of the respectivecoil since the coils are axisymmetric. Therefore, each coil, in such anembodiment, has five degrees of freedom. If at least two such coils arecombined into or integrated onto a device, such as the interventionaldevice 10, so that the coils have a known and fixed relationship to oneanother, then six degrees of freedom (x, y, z, roll, pitch, yaw) can bedetermined from the aggregate or combined information obtained form thetwo or more coils. In this way, the EM fields generated by the EM coilsmay be used to determine the position and orientation of the portion ofthe interventional device upon which they are integrated. For example,in the embodiment depicted in FIGS. 1 and 2, the sensor elements 16(which are presumed to be EM coils in this example) that are fixed onthe reference portion 14 of the catheter 20 allow the position andorientation of the reference portion 14 of the catheter 20 to bedetermined based upon the EM fields generated by the EM coils.

As described above, an interventional device 10 may be used accordancewith the present technique to allow image-guided invasive procedures. Aswill be appreciated, any imaging modality suitable for use in animage-guided interventional procedure may be employed in the presenttechnique. Examples of such imaging modalities include X-ray basedimaging techniques which utilize the differential attenuation of X-raysto generate images (such as three-dimensional fluoroscopy, computedtomography (CT), tomosynthesis techniques, and other X-ray based imagingtechnologies). Other exemplary imaging modalities suitable forimage-guided interventional procedures may include magnetic resonanceimaging (MRI), ultrasound or thermoacoustic imaging techniques, and/oroptical imaging techniques. Likewise, nuclear medicine imagingtechniques (such as positron emission tomography (PET) or singlepositron emission computed tomography (SPECT)) that utilizeradiopharmaceuticals may also be suitable imaging technologies forperforming image-guided interventional procedures. Likewise, combinedimaging modality systems, such as PET/CT systems, may also be suitablefor performing image-guided interventional procedures as describedherein. Therefore, throughout the present discussion, it should be bornein mind that the present techniques are generally independent of thesystem or modality used to acquire the image data. That is, thetechnique may operate on stored raw, processed or partially processedimage data from any suitable source.

For example, turning now to FIG. 3, an overview of an exemplarygeneralized imaging system 34, which may be representative of variousimaging modalities, is depicted. The generalized imaging system 34typically includes some type of imager 36 which detects signals andconverts the signals to useful data. As described more fully below, theimager 36 may operate in accordance with various physical principles forcreating the image data. In general, however, image data indicative ofregions of interest in a patient 38 are created by the imager 36 in adigital medium for use in image-guided interventional procedures.

The imager 36 may be operated by system control circuitry 40 whichcontrols various aspects of the imager operation and acquisition andprocessing of the image data as well as dynamic reference data acquiredusing the present techniques. In the depicted generalized embodiment,the system control circuitry 40 includes movement and control circuitry42 useful in operating the imager 36. For example, the movement andcontrol circuitry 42 may include radiation source control circuits,timing circuits, circuits for coordinating the relative motion of theimager 36 (such as with regard to a patient support and/or detectorassembly), and so forth. The imager 36, following acquisition of theimage data or signals, may process the signals, such as for conversionto digital values, and forwards the image data to data acquisitioncircuitry 44. For digital systems, the data acquisition circuitry 44 mayperform a wide range of initial processing functions, such as adjustmentof digital dynamic ranges, smoothing or sharpening of data, as well ascompiling of data streams and files, where desired. The data are thentransferred to data processing circuitry 46 where additional processingand analysis are performed. For the various digital imaging systemsavailable, the data processing circuitry 46 may perform substantialreconstruction and/or analyses of data, ordering of data, sharpening,smoothing, feature recognition, and so forth.

In addition to processing the image data, the processing circuitry 46may also receive and process motion or location information related toan anatomical region of interest, such as the depicted internal organ 48and/or lesion 50. In the depicted embodiment, an interventional device10 is placed on or near the internal organ 48 (here depicted as theliver of the patient 26). The interventional device 10, as discussedabove, is provided with numerous (for example, three or more) sensorelements 16 (see FIGS. 1 and 2) configured to provide positioninformation. In an exemplary embodiment, the sensor elements 16 are EMcoils each configured to generate a distinctive and distinguishable EMfield. In certain embodiments where the sensor elements 16 are powered,the sensor elements 16 may be connected, such as via one or moreconductive wires 52 running through the catheter, to suitable powercircuitry 54, such as an electrical power source or outlet or a suitablebattery. While in the depicted embodiment the power circuitry 54 isdepicted as being separate from the system control circuitry 40, inother embodiments the power circuitry 54 may be part of the systemcontrol circuitry 40.

In the depicted embodiment, the signals or fields generated by thesensor elements 16 are detected by one or more antennas 56. The detectedlocation information is provided to or acquired by receiver circuitry 58which in turn provides the location data to the processing circuitry 46.As discussed in greater detail below, the location data may be used inconjunction with the image data to facilitate an image-guided procedure.

The processed image data and/or location data may be forward to displaycircuitry 60 for display at a monitor 62 for viewing and analysis. Whileoperations may be performed on the image data prior to viewing, themonitor 62 is at some point useful for viewing reconstructed imagesderived from the image data collected. The images may also be stored inshort or long-term storage devices which may be local to the imagingsystem 34, such as within the system control circuitry 40, or remotefrom the imaging system 34, such as in picture archiving communicationsystems. The image data can also be transferred to remote locations,such as via a network.

For simplicity, certain of the circuitry discussed above, such as themovement and control circuitry 42, the data acquisition circuitry 44,the processing circuitry 46, and the display circuitry 60, are depictedand discussed as being part of the system control circuitry 40. Such adepiction and discussion is for the purpose of illustration only,however, and is intended to merely exemplify one possible arrangement ofthis circuitry in a manner that is readily understandable. Those skilledin the art will readily appreciate that in other embodiments thedepicted circuitry may be provided in different arrangements and/orlocations. For example, certain circuits may be provided in differentprocessor-based systems or workstations or as integral to differentstructures, such as imaging workstations, system control panels, and soforth, which functionally communicate to accomplish the techniquesdescribed herein.

The operation of the imaging system 34 may be controlled by an operatorvia a user interface 64 which may include various user input device,such as a mouse, keyboard, touch screen, and so forth. Such a userinterface may be configured to provide inputs and commands to the systemcontrol circuitry 40, as depicted. Moreover, it should also be notedthat more than a single user interface 64 may be provided. Accordingly,an imaging scanner or station may include an interface which permitsregulation of the parameters involved in the image data acquisitionprocedure, whereas a different user interface may be provided formanipulating, enhancing, and viewing resulting reconstructed images.

To discuss the technique in greater detail, a specific medical imagingmodality based generally upon the overall system architecture outlinedin FIG. 3 is depicted in FIG. 4, which generally represents an X-raybased system 70. It should be noted that, while reference is made inFIG. 4 to an X-ray based system, the present technique also encompassesother imaging modalities, as discussed above, such as MRI, PET, SPECT,ultrasound, and so forth.

In the depicted exemplary embodiment, FIG. 4 illustratesdiagrammatically an X-ray based imaging system 70 for acquiring andprocessing image data. In the illustrated embodiment, imaging system 70is a computed tomography (CT) system or three-dimensional fluoroscopyimaging system designed to acquire X-ray projection data, to reconstructthe projection data into a two or three-dimensional image, and toprocess the image for display and analysis in accordance with thepresent technique. In the embodiment illustrated in FIG. 4, X-ray basedimaging system 70 includes a source of X-ray radiation 72 positionedadjacent to a collimator 74. The X-ray source 72 may be a standard X-raytube or one or more solid-sate X-ray emitters.

In the depicted embodiment, the collimator 74 permits a stream ofradiation 76 to pass into a region in which a subject, such as thepatient 38 is positioned. The stream of radiation 76 may be generallyfan or cone shaped, depending on the configuration of the detector arrayas well as the desired method of data acquisition. A portion of theradiation 78 passes through or around the patent 38 and impacts adetector array, represented generally as reference numeral 80. Detectorelements of the array produce electrical signals that represent theintensity of the incident X-ray beam. The signals generated by thedetector array 80 may be subsequently processed to reconstruct a visualrepresentation (i.e., an image or volumetric representation) of thefeatures within the patient 38. For example, images of the internalorgan 48 may be reconstructed in the depicted embodiment.

A variety of configurations of the detector 80 may be employed inconjunction with the techniques described herein. For example, thedetector 80 may be a multi-row detector, such as a detector having eightor sixteen rows of detector elements, which achieves limitedlongitudinal coverage of the object or patient being scanned. Similarly,the detector 80 may be an area detector, such as a high-resolutionradiographic detector having hundreds of rows of detector elements,which allows positioning of the entire object or organ being imagedwithin the field of view of the system 70. Regardless of theconfiguration, the detector 80 enables acquisition and/or measurement ofthe data used in image reconstruction of the internal organ 48.

The source 72 is controlled by a system controller 84, which furnishesboth power, and control signals for examination procedures. Moreover,the detector 80 is coupled to the system controller 84, which commandsacquisition of the signals generated in the detector 80. The systemcontroller 84 may also execute various signal processing and filtrationfunctions, such as for initial adjustment of dynamic ranges,interleaving of digital image data, and so forth. In general, systemcontroller 84 commands operation of the imaging system 70 to executeexamination protocols and to process acquired data. In the presentcontext, system controller 84 also includes signal processing circuitry,typically based upon a general purpose or application-specific digitalcomputer, associated memory circuitry for storing programs and routinesexecuted by the computer (such as programs and routines for implementingthe present technique), as well as configuration parameters and imagedata, interface circuits, and so forth.

In the embodiment illustrated in FIG. 4, the system controller 84 iscoupled to a linear positioning subsystem 86 and rotational subsystem88. The rotational subsystem 88 enables the X-ray source 72, collimator74 and the detector 80 to be rotated one or multiple turns around thepatient 38. It should be noted that the rotational subsystem 88 mightinclude a gantry or C-arm apparatus. Thus, the system controller 84 maybe utilized to operate the gantry or C-arm. The linear positioningsubsystem 86 typically enables a patient support, such as a table, uponwhich the patient rests, to be displaced linearly. Thus, the patienttable may be linearly moved relative to the gantry or C-arm to generateimages of particular areas of the patient 38.

Additionally, as will be appreciated by those skilled in the art, thesource 72 of radiation may be controlled by an X-ray controller 90disposed within the system controller 84. Particularly, the X-raycontroller 90 may be configured to provide power and timing signals tothe X-ray source 72. A motor controller 92 may also be part of thesystem controller 84 and may be utilized to control the movement of therotational subsystem 88 and the linear positioning subsystem 86.

Further, the system controller 84 is also illustrated as including animage data acquisition system 94. In this exemplary embodiment, thedetector 80 is coupled to the system controller 84, and moreparticularly to the image data acquisition system 94. The image dataacquisition system 94 receives data collected by readout electronics ofthe detector 80. The image data acquisition system 94 typically receivessampled analog signals from the detector 90 and converts the data todigital signals for subsequent processing by processing circuitry 96,which may, for example, be one or more processors of a general orapplication specific computer.

As depicted, the system controller 84 also includes aposition/orientation data acquisition system 100 configured to acquireposition and orientation data from one or more antennas 102. In thedepicted embodiment, the one or more antennas 102 detect signals and/orfields generated by sensor elements 16 on an interventional device 10placed on or in the internal organ 48 undergoing imaging or in thevasculature associated with the internal organ 48. Theposition/orientation data acquisition system 100 processes signalsacquired from the antennas 102 to generate position and/or orientationinformation about the interventional device 10 which is representativeof the internal organ 48 or of vasculature associated with the internalorgan 48. The position and/or orientation information generated by theposition/orientation data acquisition system 100 may be provided to theprocessing circuitry 96 and/or a memory 98 for subsequent processing.

The processing circuitry 96 is typically coupled to the systemcontroller 84. The data collected by the image data acquisition system94 and/or by the position/orientation data acquisition system 100 may betransmitted to the processing circuitry 96 for subsequent processing andvisual reconstruction. The processing circuitry 96 may include (or maycommunicate with) a memory 98 that can store data processed by theprocessing circuitry 96 or data to be processed by the processingcircuitry 96. It should be understood that any type of computeraccessible memory device capable of storing the desired amount of dataand/or code may be utilized by such an exemplary system 70. Moreover,the memory 98 may include one or more memory devices, such as magneticor optical devices, of similar or different types, which may be localand/or remote to the system 70. The memory 98 may store data, processingparameters, and/or computer programs having one or more routines forperforming the processes described herein.

The processing circuitry 96 may be adapted to control features enabledby the system controller 84, i.e., scanning operations and dataacquisition. For example, the processing circuitry 96 may be configuredto receive commands and scanning parameters from an operator via anoperator interface 106 typically equipped with a keyboard and otherinput devices (not shown). An operator may thereby control the system 70via the input devices. A display 108 coupled to the operator interface106 may be utilized to observe a reconstructed visual representation.Additionally, the reconstructed image may also be printed by a printer110, which may be coupled to the operator interface 106. As will beappreciated, one or more operator interfaces 106 may be linked to thesystem 70 for outputting system parameters, requesting examinations,viewing images, and so forth. In general, displays, printers,workstations, and similar devices supplied within the system may belocal to the data acquisition components, or may be remote from thesecomponents, such as elsewhere within an institution or hospital, or inan entirely different location, linked to the image acquisition systemvia one or more configurable networks, such as the Internet, virtualprivate networks, and so forth.

The processing circuitry 96 may also be coupled to a picture archivingand communications system (PACS) 112. Image data generated or processedby the processing circuitry 96 may be transmitted to and stored at thePACS 112 for subsequent processing or review. It should be noted thatPACS 112 might be coupled to a remote client 114, radiology departmentinformation system (RIS), hospital information system (HIS) or to aninternal or external network, so that others at different locations maygain access to the image data.

The systems and devices described above may be utilized, as describedherein, to provide dynamic referencing for a region of a patientundergoing an interventional procedure. In an exemplary embodiment,dynamically acquired position and orientation data for the region of thepatient may be acquired using the interventional device 10 and sensorelements 16 and this data may be automatically registered withconcurrently or previously acquired image data without the use ofanatomical or fiducial markers. In this way, the interventionalprocedure may be performed or guided based upon the dynamicallyreferenced visual representation.

For example, referring to FIG. 5, exemplary acts corresponding to oneimplementation of the present technique are provided. In theimplementation depicted in FIG. 5, the image data 122 is acquired (Block120) prior to the invasive procedure. As noted above, the image data 122may be acquired using one or more suitable imaging modalities, such asthree-dimensional fluoroscopy, CT, MRI, and so forth. In the depictedembodiment, the image data 122 is used to generate (Block 124) one ormore visual representations, such as images or volumes 126, of theinternal organ 48 (see FIG. 2) or and/or associated vasculature. In anexemplary embodiment, the image data 122 is acquired after introductionof a contrast agent to the patient's bloodstream, thereby providing goodcontrast for the vasculature in the image data 122.

The images or volumes 126 are segmented (Block 128) in the depictedimplementation to provide one or more segmented regions 130. Such asegmentation process typically identifies pixels or those portions of animage representing common structures, such as organs, tissues,vasculature, and so forth. For example, a segmentation a process mayidentify surfaces or boundaries defining an organ, tissue, or bloodvessel (such as by changes in intensity or some other thresholdcriteria). In this way, all of those pixels representing respectiveorgans, tissues or blood vessels, portions of such organs, tissues orblood vessels, or regions proximate or connected to such organs,tissues, or blood vessels, may be identified and distinguished from oneanother, allowing processing or evaluation of only the portions of animage associated with the organs, tissues, or blood vessels of interest.For example, in an embodiment where contrast agents are employed and theliver and hepatic vasculature are the region of interest, the hepaticvein can be segmented in the images and/or volumes 126. In this manner,a geometric or spatial model of the segmented hepatic vein can begenerated for subsequent procedures, as described below.

The images or volumes 126 may be segmented using known segmentationtechniques, such as intensity and/or volume thresholding, connectivityclustering, and so forth. In one embodiment, the segmentation allows theorgan, tissue, blood vessel, or other region of interest to begeometrically or spatially modeled, as noted above. In an exemplaryembodiment, the segmented region corresponds to the internal organ 48 orblood vessel within which the interventional device 10 (see FIGS. 1 and2) will be placed for dynamic referencing. While the depicted actionsdescribe an embodiment in which images or volume 126 generated from theacquired image data 122 are segmented, in other embodiments thesegmentation may be performed on the image data 122 itself, with thesegmented image data being subsequently used to generate images orvolume of the internal organ 48, blood vessel, or other region ofinterest. Based upon the segmented image or volume of the internal organor blood vessel, i.e., the segmented region 130, a model 134 of theregion is generated (Block 132) which generally corresponds to theinternal organ 48, blood vessel, or other region of interest asdeterminable form the imaging process.

In some embodiments, the region model 134 may incorporate image dataacquired using more than one type of imaging modality. For example, insome embodiments, it may be desirable to use image data derived formboth an MRI system and an X-ray based imaging system, such as athree-dimensional fluoroscopy system. In such an embodiment, the signalsacquired by both system may be registered, as discussed below, such thatthe combined images and/or volumes 126, segmented region 130 and/orregion model 134 consists of or is representative of the imageinformation acquired by each imaging modality.

During the invasive procedure performed on the internal organ 48 (orother region of interest), the interventional device 10 is placed (Block140) in, on, or near the internal organ 48, such as in the vasculatureleading to the internal organ 48. As noted above, the interventionaldevice 10 includes at least three sensor elements 16, which in oneembodiment, are provided on a reference portion 14 of the interventionaldevice 10. The sensor elements 16 generate respective signals (such asrespective EM fields) which may be acquired (Block 142) or measured toderive position and/or orientation data 144 for each respective sensorelement 16. The position and/or orientation data 144 may be used togenerate (Block 146) a device model 148 representing shape, positionand/or orientation of the interventional device 10.

The device model 148 derived from the position and/or orientation data144 is registered (block 150) with the region model 134 generated usingthe imaging process. In an exemplary embodiment, the registration of thedevice model 148 and the region model 134 is accomplished automatically,such as using iterative closest point techniques. In this manner, thesensor elements 16 of the interventional device 10 are automaticallyregistered to the images of the region of interest, i.e., the internalorgan 48 and/or associated vasculature, thereby allowing the positionand/or orientation of the internal organ 48 or associated vasculature tobe modified in a visual representation based on the most recent positionand/or orientation data from the sensor elements 16 of theinterventional device.

An image-guided invasive procedure may be performed using the registereddevice model 148 (based on the position and/or orientation data) andregion model 134 (based on the image data). In particular, once thepreviously acquired image-based information or model is registered tothe measured position and/or orientation data, changes in the positionand/or orientation data can be used to visually indicate changes to theimage-based model. In other words, a displayed image of the internalorgan 48 or the associated vasculature may be updated, modified,altered, or otherwise, changed, based on the most current positionand/or orientation data obtained from the sensor elements 16 of theinterventional device 10. In this way, even though no imaging processesare occurring during the operation, the previously acquired image datacan be updated and manipulated to provide an accurate and currentrepresentation of the internal organ and/or associated vasculatureundergoing the procedure.

Based on this registration between the region model 134 (derived theimage data) and device model 148 (derived from the sensor element data),an interventional tool may be tracked (Block 152) during aninterventional procedure. Examples of such interventional tools that maybe tracked include biopsy needles, catheters, ablation needles, and soforth. Typically the interventional tool being tracked also includes asensor element 16, such as an EM sensor, so that position and/ororientation information for the interventional tool is also acquired,thereby allowing the position of the interventional tool to be displayedin conjunction with the registered image of the moving and/or deformedinternal organ 48 or the vasculature of such an organ. In this manner, asystem such as those described herein, may display to a user inreal-time or substantially real-time the location of the interventionaldevice relative to the moving and/or deformed internal organ 48 or itsvasculature.

While the preceding described an implementation in which the imagingprocedure is performed prior to the interventional procedure, in otherimplementations the imaging procedure is performed concurrently with theinterventional procedure. For example, referring to FIG. 6, actsassociated with a further exemplary embodiment of the present techniqueare depicted. In this embodiment, a reference portion 14 of aninterventional device 10 is placed (Block 156) in or near an internalorgan 48 of interest, such as the vasculature leading to the internalorgan 48. Position and/or orientation data 160 is acquired (Block 158)for the sensor elements 16 integrated on the reference portion 14. Forexample, in embodiments where the sensor elements 16 generate EM signalsor fields, these signals or fields can be detected and/or measured, suchas using one or more antenna arrays as described above, to derive aposition and/or orientation for each respective sensor element 16.

In the depicted embodiment, image data 122 is acquired (Block 120) andis used to generate (Block 124) one or more images and/or volumes 126.Some or all of the sensor elements 16 are located (Block 162) in theimages and/or volumes 126 such that the position data 164 for therespective sensor elements 16 is obtained with respect to theimages/volumes 126. In an exemplary embodiment, the sensor elements 16are automatically located in the images/volumes 126. For example, thesensor elements 16 may be automatically located using image processingtechniques such as intensity and/or volume thresholding, connectivityclustering, template matching, and so forth. In addition, in someembodiments, the positions of the sensor elements 16 are known withrespect to one another based on the measured signals or fields generatedby the sensor elements 16. This sensor derived position data 158 may beused to find the sensor elements 16 in the images and/or volumes 126.

Once some or all of the sensor elements 16 are identified in the imagesand/or volumes, the positions 164 of the sensor elements 16 located inthe images and/or volumes may be matched (Block 166) to thecorresponding sensor element locations as determined from the sensorposition data 160. In other words, the sensor elements 16 located in theimages and/or volumes are matched with the corresponding sensor elementssignals and/or fields generated by the sensor elements 16. In oneembodiment, this may be facilitated by using different sizes of sensorelements 16 on the interventional device 10 such that the sensorelements 16 can be distinguished in the image data and matched to theircorresponding sensor signals. Likewise, a priori information aboutpatient position in the images may be used to determine which sensorelement 16 is the element and which is the proximal one, therebyallowing matching between the sensor element readings and the identifiedsensor elements 16 in the images. Alternatively, a sufficiently largenumber (i.e., four or more) of sensor elements 16 may be provided in oneembodiment such that all possible matches may be permuted and the matchgenerating the smallest registration error is selected as the correctmatch or correspondence.

Based on the established or possible correspondences, the sensor elementpositions derived using the sensor data and the imaging data areregistered (Block 168). As noted above, in some embodiments, theregistration and the establishment of the correspondences may actuallydepend on one another, i.e., the registration errors associated withdifferent possible matches may be used to select the correctcorrespondence. In one embodiment the centroid of each sensor element 16as determined in the images and/or volumes is registered to thecorresponding sensor element signal in the position data derived fromthe sensor elements 16. In certain implementations the registration canbe accomplished using iterative optimization techniques or a closed formsolution. As noted above, in certain embodiments, to obtain a uniqueregistration it is generally desired that the three or more sensorelements not lie on or near a straight line. In certain embodiments,such as in an embodiment where the interventional device 10 is acatheter configured for insertion into the hepatic artery, theinterventional device may be designed so that the sensor elements 16 arestructurally prevented from being collinear, i.e., the reference portion14 may be curved. In other embodiments, such as where the sensorelements 16 are not structurally prevented from being collinear,feedback may be provided to the user in the event that a uniqueregistration can not be determined and the user can adjust the positionof the interventional device 10 until a unique registration is obtained.

Once the sensor elements 16 are registered in both the sensor space(such as EM space) and the image space, the interventional procedure maybe performed using the dynamic tracking of the internal organ based uponthe signals from the sensor elements 16. For example, no further imagingmay be performed or the image data may be updated only sporadically,with other updates to the images used in the interventional procedurebeing based upon the continuous, substantially real-time tracking of thesensor elements 16. In this way, even though imaging does not occur oroccurs only sporadically during the operation, the displayed images canbe updated and manipulated to provide an accurate and currentrepresentation of the internal organ 48 (or other internal region)undergoing the procedure.

In one implementation an interventional tool may be tracked (Block 152)during an interventional procedure, using images updated based upon theposition data derived form the sensor elements and the registration ofthese signals with the image and/or volumes 126. Examples of suchinterventional tools that may be tracked include biopsy needles,catheters, ablation needles, and so forth. Typically the interventionaltool being tracked also includes a sensor element 16, such as an EMsensor, so that position and/or orientation information for theinterventional tool is also acquired, thereby allowing the position ofthe interventional tool to be displayed in conjunction with the imageupdated using the position data for the sensor elements 16. In thismanner, a system such as those described herein, may display to a userin real-time or substantially real-time the location of theinterventional tool relative to the moving and/or deformed internalorgan 48.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. An interventional device comprising: a reference portion configuredfor placement proximate to or inside an internal organ such that thereference portion moves with the internal organ, wherein the referenceportion is not physically attached to the internal organ when so placed;and three or more sensor elements integrated on the reference portion,wherein the three or more sensor elements are configured to provide atleast position information.
 2. The interventional devise of claim 1wherein the interventional device comprises a catheter.
 3. Theinterventional device of claim 1 wherein the three or more sensorelements comprise three or more electromagnetic sensor coils.
 4. Theinterventional device of claim 1 comprising one or more receivingcomponents configured to detect positional and/or directional signalsgenerated by the three or more sensor elements.
 5. The interventionaldevice of claim 1 comprising one or more antennas configured to detectelectromagnetic fields generated by the three or more sensor elements.6. The interventional device of claim 1 comprising one or moretransmitters configured to generate electromagnetic fields detectable bythe three or more sensor elements.
 7. The interventional device of claim1 wherein the reference portion comprises a terminal region of theinterventional device.
 8. The interventional device of claim 1 whereineach sensor element provides position information in three dimensionsand orientation information in two directions.
 9. The interventionaldevice of claim 1 wherein the three or more sensor are in fixed relationto one another such that the combination of the three or more sensorelements provide position information in three dimensions andorientation information in three directions.
 10. The interventionaldevice of claim 1 comprising a power supply electrically connected tothe one or more sensor elements.
 11. The interventional device of claim1 wherein the three or more sensor elements are not substantiallycollinear.
 12. A method for tracking dynamic motion of an organcomprising the acts of: generating a first set of position data forthree or more sensor components integrated on a reference portion of aninterventional device, wherein the reference portion is placed proximateto or inside of an internal organ and wherein the first set of positiondata is based on signals or fields generated by the sensor components;generating a second set of position data for the three or more sensorcomponents based on an identification of the three or more sensorcomponents in one or more images or volumetric representations of theinternal organ; identifying corresponding sensor components in the firstset of position data and the second set of position data; andregistering the first set of position data with the one or more imagesor volumetric representations based on the identification ofcorresponding sensor components in the first set of position data andthe second set of position data.
 13. The method of claim 12 comprisinggenerating the one or more images or volumetric representations based onimage data acquired using at least one of computed tomography,ultrasound, magnetic resonance imaging, or three-dimensionalfluoroscopy.
 14. The method of claim 12 wherein at least one ofgenerating the first set of position data, generating the second set ofposition data, identifying corresponding sensors, or registering thefirst set of position data with the one or more images or volumetricrepresentations is performed automatically.
 15. The method of claim 12comprising tracking an interventional tool using the registered firstset of position data and the one or more images or volumetricrepresentations.
 16. A method for tracking dynamic motion of an organcomprising the acts of: generating a position and orientation data forthree or more sensor components integrated on a reference portion of aninterventional device, wherein the reference portion is placed proximateto or inside of an internal organ and wherein the position andorientation data is based on signals or fields generated by the sensorcomponents; generating a shape model of the interventional device basedon the position and orientation data; segmenting a region of interest inone or more images or volumetric representations, wherein the region ofinterest comprises at least one of the internal organ, a portion of theinternal organ, or a region proximate or connected to the internalorgan; generating a shape model of the region of interest based on thesegmentation; and registering the shape model of the interventionaldevice and the shape model of the region of interest.
 17. The method ofclaim 16 comprising generating the one or more images or volumetricrepresentations based on image data acquired using at least one ofcomputed tomography, magnetic resonance imaging, ultrasound, orthree-dimensional fluoroscopy.
 18. The method of claim 16 wherein atleast one of generating the position and orientation data, generatingthe shape model of the interventional device, segmenting the region ofinterest, generating the shape model of the region of interest, orregistering the shape model of the interventional device and the shapemodel of the region of interest is performed automatically.
 19. Themethod of claim 16 comprising tracking an interventional tool using theregistered shape model of the interventional device and shape model ofthe region of interest.
 20. The method of claim 16, wherein the regionof interest comprises one or more blood vessels servicing the internalorgan.